The watchdog position was created by a voter-approved ballot measure in 2009, partly in response to soaring settlement costs in employee harassment and discrimination lawsuits at the department.

Miller, a lawyer, was the first person to hold the job. During his tenure, he issued audits critical of how the department handled lawsuits and internal investigations. Last year, he clashed with fire officials and union leaders about access to sensitive personnel records.

His dismissal is the latest in a series of changes at the LAFD under Garcetti. Last week, he announced that he and Fire Chief Brian Cummings had reached a "mutual agreement" for Cummings to step down. Earlier, Garcetti replaced four of the city's five commissioners on a civilian board that oversees the department.

Confidence in the LAFD's management slumped after fire officials admitted last March to miscalculating emergency-response times, making it appear that rescuers arrived more quickly than they actually did.

Subsequent investigations by The Times documented widespread delays in processing calls for help, routine failures to summon the closest medical rescuers from nearby jurisdictions and large disparities in the time it takes rescuers to get to life-threatening emergencies in different areas of the city.

Miller did not respond to requests for an interview. Fire Commissioner Andrew Glazier, a Garcetti appointee, declined to say why Miller was removed and said there was no timetable for appointing a replacement. The decision was made during a closed session and without public debate.

"This job is critical to our ability to do our work," Glazier said. "We'll be looking for somebody who brings expertise and ability to do our job and be the best department we can be."

A spokeswoman for Garcetti declined to comment. But the head of the union that represents rank-and-file firefighters welcomed Miller's departure. The union strongly opposed Miller's effort to review confidential personnel records as part of his investigations.

"He ran rogue and to the beat of his own drum and he tried to exceed the original intent of the position," said Capt. Frank Lima, president of United Firefighters of Los Angeles.

The independent assessor reports to the Fire Commission and has a duty under the law to review the handling of allegations of misconduct by LAFD employees.